Traditionally, a user can utilize an emergency call box to communicate with an emergency dispatch operator using voice communication. Generally, emergency call boxes have not been provided with Telecommunications Devices for the Deaf (TDD) or Text Telephony (TTY) capability. Thus, a user who is deaf, hearing-impaired, or speech-impaired may not be able to communicate with an emergency dispatch operator. The difficulties experienced by a hearing-impaired user are also aggravated by the fact that many emergency call boxes are located in extremely noisy roadside environments.
To overcome these drawbacks, emergency call boxes with TDD or TTY capability have been developed. Call boxes have been equipped with a TDD keypad that is permanently attached on the outside of the call box to enable a user to bidirectionally communicate with an emergency dispatch operator without the need for voice communication. However, these keypads are vulnerable to damage due to harsh environments. In addition, vandalism of these keypads poses a major problem.
To overcome these drawbacks, emergency call boxes with a keypad contained within the call box or with a retractable keypad assembly attached outside of the call box have been developed. However, these keypads are flat and located in a non-ergonomic position, thus hindering use by persons of various heights and in wheelchairs.
Traditionally, lead screws have been used to extend and retract flat trays or other members in a linear direction parallel to the axis of the lead screw. However, flat trays, even if not deployed horizontal to the ground, are not ergonomically adapted for a person's use. Therefore, traditional lead screws are unable to deploy an ergonomic tray to an ergonomic position in order to accommodate use by persons of various heights and in wheelchairs.